The present invention relates to graphic equalizers with spectrum analyzers and systems thereof and more particularly to a graphic equalizer which is provided with a spectrum analyzer for displaying the spectrum of a signal, and which varies and adjusts the level of the signal for every divided frequency band as the spectrum display is observed and to a system for employing the graphic equalizer.
In general, it is desirable in some instances in the recording of an audio signal, when there is a sound unpleasant to the ear such as noise or the sound of the wind of a low constant frequency, to carry out the recording of the audio signal with lowered level of the frequency band in which these sounds are present. In the case where, in a reproducing apparatus, the fidelity of the reproduced audio signal is impaired by the effects of characteristics such as the frequency characteristics possessed by the audio components themselves such as the loudspeakers and the pickup cartridge and the transmission characteristic of the listening room, it is desirable in some instances to correct the level of a certain frequency band. Furthermore, there are instances where, in both recording and reproducing, the frequency characteristics are rendered into desired characteristics according to preference without flattening the frequency characteristics. In such cases, a graphic equalizer capable of variably adjusting the level of the signal for every divided frequency band is used.
Among graphic equalizers, there are those provided with a calibrated scale for indicating the adjustment level interrelatedly with the movement of a manipulating knob for adjusting the level for every band. In such a graphic equalizer, however, the degree of level adjustment with respect to the input signal can be determined, but the level of the signal after level adjustment cannot be accurately determined.
Accordingly, in accordance with the present invention, a spectrum analyzer is integrally incorporated within a graphic equalizer so that level adjustment can be carried out as the spectrum of the signal after it has passed through the graphic equalizer is observed. By this organization, since the level adjustment can be carried out as the level of the signal which has been actually adjusted is observed, the level adjustment can be carried out rapidly and accurately.
However, when the divided frequency bands which have been level adjusted by the graphic equalizer and the divided frequency bands indicated by the spectrum analyzer are different, accurate level adjustment cannot be carried out. Accordingly, according to the present invention, the center frequencies respectively of the divided frequency bands level adjusted by the graphic equalizer and the center frequencies respectively of the divided frequency bands indicated by the spectrum analyzer are caused to coincide. Furthermore, on the face of the manipulative control and indication display panel of the apparatus, the level adjustment control elements and the indication display units of the spectrum analyzer are disposed in respectively corresponding dispositions. By this arrangement, level adjustment can be carried out readily and accurately.
Still another difficulty arises in certain cases wherein, even when the frequency characteristics of the signal to be emitted as sound from the loudspeakers are satisfactory, the frequency characteristics of the sound emitted from the loudspeakers and actually reaching the ears of the listener in the sound field become different from the above mentioned satisfactory frequency characteristics in accordance with the characteristics of the sound field including also the characteristics of the loudspeakers.
Accordingly, in accordance with the present invention, means are provided and adapted to make possible adjustment so that the frequency characteristics of the actual sound at the listening position of the listener will become the desired frequency characteristics. For this purpose, the spectrum of the sound at the listening position of the listener is indicatively displayed by the spectrum analyzer, and level adjustment of the input audio signal is carried out by the graphic equalizer as the spectrum thus displayed is observed.
In addition, there are cases wherein only the transmission characteristic of a signal transmission system is known, and it is desired to transform this into a desired characteristic. The level of an ordinary input audio signal is continually fluctuating in every frequency band. Accordingly, in accordance with the present invention, a pink noise of equal energy distribution irrespective of frequency band is used in the adjustment of the transmission characteristic of the signal transmission system to the desired value.